Ferdinand a



(No Model.)

F. A. WESSEL.

SWITCH FOR ELECTRIC MOTORS.

No. 453,318. Patented June 2,1891.

lNvEN T i Tend/mud W088 65 .JTMOTW UNITE STATES PATENT OFFICE.

FERDINAND A. VESSEL, OF BROOKLYN, ASSIGNOR TO THE EXCELSIOR ELECTRIC COMPANY, OF NEIV YORK, N. Y.

SWITCH FOR ELECTRIC MOTORS.

SPECIFICATION forming part of Letters Patent No. 453,318, dated June 2, 1891.

Application filed January 9. 1891.

To all whom it may concern.-

Be it known that I, FERDINAND A. VESSEL, a citizen of the United States, and a resident of Brooklyn, in the county of Kings and State of New York, have invented a certain new and useful Improved Switch for Electric Motors, of which the following is a specification.

My invention relates to starting-switches for electric motors, and specially motors fed from constant-potential wires.

The object of my invention is to prevent damage to the motor by a sudden flow of excessive current through the same. hen a motor-armature revolves at a slow rate of speed, its counter electro-motive force is small, and hence it offers very little resistance to the flow of current through it. As the speed rises, the counter electro-motive force gradually rises also until when the normal speed has been attained there will be a normal flow of current through such armature. It is, moreover, well known that an increase of load will reduce the speed of the armature, and in reducing its counter electro-motive force will give rise to the flow of an abnormally strong current therethrough. The effect of this abnormally strong current passing through the armature when its speed is slow, either at starting or from overloading or any other cause, is the great liability to burn the armature before it attains the requisite speed. To prevent this destructive tendency, it has been customary heretofore to provide an artificial resistance placed into the armature connection and gradually thrown or cut out as the speed rises by a switch-lever operated by hand.

My present invention is designed to remove the necessity of manipulating the switch-lever by hand, which heretofore existed; and for this purpose the same consists in a starting rheostatic switch in the armature connection automatically operated by the armature actuated by the field-magnet of the motor and adapted to cut out the resistance as the speed of the armature rises. I

In my present invention I take advantage of the fact that the armature of the machine if out of central position or position of equilibrium with regard tothe magnetic field will be drawn into said field or into a position Serial No. 377,268. (No model.)

where there will be an equilibrium of the magnetic forces. The rheostatic switch or protective resistance is controlled by the movements of the armature and shaft prod uced through this centering tendency, movement in one direction being brought about by the movement due to the magnetic force tending to center the armature and movement in the other direction being produced by the action of a spring or other opposing influence or force.

My invention provides an effective safeguard against damage to the motorfrom stoppage through overloading or from other cause when an attendant is not at hand to throw the motor out of operation.

My invention, moreover, consists in such further features, details of construction, and combinations of parts as will be hereinafter enumerated and pointed out in the claims.

I11 the accompanying drawing I have shown what Iconsider the best means of carrying my-inventioninto effect.

In the drawing, the figure is a diagrammatic representation of an organization embodying theinvention.

mm aretheconstantpotentialmainsfeeding the motor.

F is the usual field-magnet, and A the usual rotary armature, included in the connection 5, which leads from one main through the brushes B B and the said armature and also through the artificial resistance r and switch lever or arm Z, together constituting the starting or rheostatic switch, and thence to the other main 412. As shown, the leverZ is insulated at ifor obvious reasons.

At 8 is shown the usual main switch, which serves to throw the motor in or out of circuit.

The armature A is mounted in journalsjj, adapted to slide in their bearings, and at one end it is connected by apivot p or otherwise to the switch-lever Z, so as to cause the said lever or arm to move when the armature slides in its bearings. This movement is preferably imparted to the said lover or arm by having the same fulcrumed atfto a link Z, supported by the motor-frame f. In order to push the armature and its journal back to their extreme position when no current is passing through the field-magnets, I con ncct some part connected to the sliding journals, preferably the lever l, to the frame by a retracting-spring s. In order to retard the sliding motion of the armature under the centering influence of the field-magnet F when the current is started, and hence to retard the movement of the switch-lever Z so as not to cutout the resistance 0' before or faster than the armature acquires the requisite speed, 1 connect the lever Z with a suitable retarding devicesuch as a dash-pot (Zwhose piston d ishere connected with said lever by bell-crank d and arm (1 The operation of the apparatus so far described is as follows: \Vhen it is desired to start the motor, the switch-lever s is turned so as to close the circuit and to energize the field-magnets F. The armature slowly begins to revolve. At this stage of the operation, when by reason of its small speed the armature produces but a slight counter-current to the high potential current passing through the mains, the passage of this full current, and the consequent injury to the armature, is prevented by the resistance '2', all of whose coils are included in the shunt-circuit s at starting. The field-magnet, however, at once tends to center the armature A and shift it to the left in the figure. This tendency is controlled by the retarding device, in the present instance a dash-pot d, which retards the centering operation, and consequently the movement of the rheostatic switch-lever Z, so that sufficient time will have elapsed for the armature to attain its normal speed before the coils of the resistance 1 have all been out out, so as to enable the current to flow directly through the shunt-wire s. As soon as the flow of current ceases, the spring 5 returns the lever Z to its initial position and interposes the full resistance into the shunt-circuit, so that on starting the operation described will be re peated.

lVhat I claim as my invention is- 1. The combination, with an electric motor, of an armature for the same normally out of central or neutral position in the magnetic field, and a rheostatic switch placed in the armature-circuit and operated or controlled by the end movement of the armature-shaft, due to the centering tendency of the fieldmagnet when the motor is thrown into operation.

2. The combination, with an electric motor run from a constant-potential main, of a rotary armature operated by field-magnets and normally out of the magnetic center of the field, a shaft for said armature, having an end movement, and a rheostatic switch the whole or a greaterpart of whose resistance is in the armature-circuit when the machine is at rest or running at low speed, said rheostatic switch bcin g controlled or operated by the end movement of the shaft when the machine is thrown into operation, whereby the resistance may be greatly cut out as the sgeed rises.

3. The combination, in an electric motor run from a constant-potential main, of a sliding armature, a spring tending to hold such armature out of central position in the magnetic field, and a rheostatic switch in the armature-circuit, havingits operating-lever or equivalent part connected to the armature, as and for the purpose described.

4:. In an electric motor, the combination of a rotary and sliding armature with a rheostatic switch the whole or a greater part of whose resistance is in the armature-circuit when the motor is at rest or running at slow speeds, said switch being connected to the sliding armature, so as to be operated by the same to gradually cut out the resistance as the speed of the armature rises.

5. The combination,in an electric motor, of a sliding armature, a rheostatic switch the whole or a greater part of whose resistance is in the armature-circuit when the machine is at rest or running at slow speed, and a dashpot or retarding mechanism connected with said armature and rheostatic switch, as and for the purpose described.

6. The combination, with an electric motor having its armature mounted on a sliding shaft, of a rheostatic protective switch in the armature connections, a field-magnet which tends to pull the armature and shaft in one direction longitudinally, a spring or retractor which tends to move it in the other, and a switch-lever or equivalent mechanism actuated by said armature-shaft.

7. In an electric motor, the combination, with an armature in a connection between the constantpotential mains and a rheostatic switch the whole or a greater part of whose resistance is in the armature-circuit when the motor is at rest or running at slow speed, of a switch-lever actuated by said armature through the centering tendency of the fieldmagnet on the end movement of the armatureshaft produced thereby, a spring tendin g to move said switclrlever in the opposite direction, and a dash-pot or retarding mechanism, as and for the purpose described.

8. In an electric motor, the combination of an armature operated by the field-magnet and a rheostatic switch connected with the armature, having its resistance in the armatureshunt and adapted to be actuated by the said armature, so as to gradually cut out the resistance as the speed of the armature rises, substantially as shown and described.

Signed at New York, in the county of New York and State of New York, this 27th day of December, A. D. 1890.

FERDINAND A. \VESSEL.

Witnesses:

WM. H. CAPEL, T. F. Coun er.

IIO 

